My argument in favor of the dissenting view (Gray’s) is this. When Elmer murdered his grandfather, the law prohibiting this has already failed in its function, viz., to deter murders.
In fact, it is possible that Elmer knew all the ins and outs of this part of criminal law and counted deviously on the very fact that even if he is caught, the judge would have to, as per the letter of the law, let him keep the inheritance!
We may imagine Elmer making this calculation and deciding to proceed with his evil scheme.
Therefore, the failure lies in the higher ruling principle of the defective legal system. But it is not the task of judges to repair laws by laying down their own arbitrary notions. Laws are made by the people and their representatives, not by the judicial aristocracy.
It would seem that Elmer would have gotten away with his crime. But it would merely have been a symptom of the disease. What could have happened was that Elmer’d be allowed to keep the money, and then the legislature, in the next session, scandalized and embarrassed by the case, would so alter the law as to take future Elmer wannabes into account. By trying to “fix” the defect, the judges treated the symptoms, seemingly satisfying our sense of justice but also eliminating the incentives for the legislators to improve the law.
The judges should have used precisely “mechanical” jurisprudence and left lawmaking to the lawmakers. Elmer would keep his ill-gotten gains on a technicality, but it would alert the legislative branch of the state of the problem and thrust them into action to repair the legal system.